Function of Core Unit as a Resource to the Program Project Grant. Histology Core Overview This Histology Core analyses tissues from genetically manipulated mice and from littermate controls, in collaboration with the Research Units of this Program Project, using various histochemical and immunohistochemical assays. Tissues from normal littermate controls are compared with those obtained from genetically altered mice, to identify specific changes in phenotype as evidenced by changes in morphology or changes in binding to a variety of probes (e.g., antibodies or lectins). Histology is crucial for providing the prerequisite morphologic data on any sample of organ or tissue, prior to the use of the excised tissue in different analytical assays. Histological examination of tissue thus establishes the absence of abnormal pathology, such as inflammation, necrosis, hemorrhage or tumor, prior to using the extracts of the tissue in various experiments. Scientific investigation of the role of particular genes in cancer is very often dependent on the ability to translate observations obtained from methods such as enzyme linked immunosorbent assays, polymerase chain reaction or even Northern, Southern, Western blots, into identifying the cell types of expression in tissue sections. The analysis of single cells by flow cytometry, or even the analysis of tissue sections with confocal microscopy is facilitated by the use of confirmatory histological methods. Very often, it is the expression of gene products in a particular tissue that allows the investigator to deduce the significance of its presence, to its function. The results obtained from analysis of tissue are also critical in the planning of future directions of projects.